The invention relates to a charging and discharging device for heating furnaces, especially continuous bogie hearth furnaces and rotating hearth furnaces.
Charging and discharging machines for continuous bogie hearth furnaces and rotating hearth furnaces are known, and these have liftable or pivotable manipulator arms with lifting forks or tongs.
The manipulator arms and lifting forks partially project with their active region from the suspension supporting them, to such an extent that they are lowered somewhat, via this region and thereby, when the material to be heated is transferred to the individual hearth bogies or onto the beds of the rotating hearth furnace, release the individual slabs, billets or the like so that they are tilted, with the result that they first come up against the ceramic bed by one edge only and can very easily damage the bed as a result of the surface pressures arising thereby. When two slabs, billets or the like are seized directly in succession by the charging device and also released at the same time, under certain circumstances, the second billet or the like, when transferred to the ceramic bed, can hang freely in the air while the first billet already touches the bed, with the result that the second billet covers a certain distance in freefall before it strikes the ceramic bed. The possible damage to the ceramic beds which arises thereby results in long shutdown and repair times and consequently high costs.
The smaller the lifting height and traveling distances of devices of this type can be made, the simpler becomes the sealing off from the furnace walls, which is absolutely necessary to ensure as low heat losses as possible. Also, it is possible to maintain rapid cycle times more easily. Moreover, less drive and braking power is required.
A disadvantage of the gripping tongs which are sometimes used is that the material to be heated must be positioned on the hearth bogies or on the beds of the rotating hearth furnaces at a relatively great distance, so that the gripping tongs of the charging and discharging devices can pass through between the individual parts of the deposited material to be heated and can grasp individual billets or the like. Particularly in rotating hearth furnaces, in which these distances have to be ensured between in individual billets or the like even in the inner radius of the rotating hearth, this results in an undesirably large unoccupied area of the rotating hearth, especially in the outer regions.
The feed systems for the proposed charging and discharging devices are relatively expensive because of the use of lifting prisms or the like.
The following is based, in particular, on a charging and discharging device with one or more vertically and longitudinally movable supporting arms.
The requirements for maintaining short cycle times, low heat losses, the gentlest possible depositing of the material to be heated on the ceramic beds and simple design and operation are each only partially satisfied by the known devices.